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author | Ben Cheng <bccheng@google.com> | 2014-03-25 22:37:19 -0700 |
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committer | Ben Cheng <bccheng@google.com> | 2014-03-25 22:37:19 -0700 |
commit | 1bc5aee63eb72b341f506ad058502cd0361f0d10 (patch) | |
tree | c607e8252f3405424ff15bc2d00aa38dadbb2518 /gcc-4.9/libgo/go/math/acosh.go | |
parent | 283a0bf58fcf333c58a2a92c3ebbc41fb9eb1fdb (diff) | |
download | toolchain_gcc-1bc5aee63eb72b341f506ad058502cd0361f0d10.tar.gz toolchain_gcc-1bc5aee63eb72b341f506ad058502cd0361f0d10.tar.bz2 toolchain_gcc-1bc5aee63eb72b341f506ad058502cd0361f0d10.zip |
Initial checkin of GCC 4.9.0 from trunk (r208799).
Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba
Diffstat (limited to 'gcc-4.9/libgo/go/math/acosh.go')
-rw-r--r-- | gcc-4.9/libgo/go/math/acosh.go | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/gcc-4.9/libgo/go/math/acosh.go b/gcc-4.9/libgo/go/math/acosh.go new file mode 100644 index 000000000..e394008b0 --- /dev/null +++ b/gcc-4.9/libgo/go/math/acosh.go @@ -0,0 +1,60 @@ +// Copyright 2010 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package math + +// The original C code, the long comment, and the constants +// below are from FreeBSD's /usr/src/lib/msun/src/e_acosh.c +// and came with this notice. The go code is a simplified +// version of the original C. +// +// ==================================================== +// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. +// +// Developed at SunPro, a Sun Microsystems, Inc. business. +// Permission to use, copy, modify, and distribute this +// software is freely granted, provided that this notice +// is preserved. +// ==================================================== +// +// +// __ieee754_acosh(x) +// Method : +// Based on +// acosh(x) = log [ x + sqrt(x*x-1) ] +// we have +// acosh(x) := log(x)+ln2, if x is large; else +// acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else +// acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1. +// +// Special cases: +// acosh(x) is NaN with signal if x<1. +// acosh(NaN) is NaN without signal. +// + +// Acosh returns the inverse hyperbolic cosine of x. +// +// Special cases are: +// Acosh(+Inf) = +Inf +// Acosh(x) = NaN if x < 1 +// Acosh(NaN) = NaN +func Acosh(x float64) float64 { + const ( + Ln2 = 6.93147180559945286227e-01 // 0x3FE62E42FEFA39EF + Large = 1 << 28 // 2**28 + ) + // first case is special case + switch { + case x < 1 || IsNaN(x): + return NaN() + case x == 1: + return 0 + case x >= Large: + return Log(x) + Ln2 // x > 2**28 + case x > 2: + return Log(2*x - 1/(x+Sqrt(x*x-1))) // 2**28 > x > 2 + } + t := x - 1 + return Log1p(t + Sqrt(2*t+t*t)) // 2 >= x > 1 +} |